Alkaloid compounds and their use as anti-malarial drugs

ABSTRACT

Anti-malarial alkyloid compounds have the formula: 
                         
wherein R 1 -R 11  have various disclosed values or their pharmaceutically acceptable salts, and pharmaceutical compositions containing the same.

The present invention concerns alkaloid compounds and their use as a medicament. These compounds and derivatives are particularly useful against malaria in a prophylactic and/or curative treatment. Therefore, the present invention also concerns pharmaceutical compositions comprising the new compounds and the use of the compounds in a process for the preparation of anti-malarial compositions. Furthermore in another aspect of the invention, it concerns a process of preparation of these compounds.

Malaria is a serious health care problem posing a great menace to society due to the number of patients infected and the mortality rate of patients, as evidenced by about 300 million patients attacked annually predominantly in tropical and subtropical regions, causing about 2 million deaths in these areas.

Malaria is usually treated by administering chloroquine, pyrimethamine, quinine, proguanil, primaquine, artemisinin compounds, etc. . . . , even combinations thereof, but effective treatments have become difficult with these conventional anti-malarial drugs because most of the malarial parasites eventually become resistant to these anti-malarial drugs. Most of the usual anti-malarial compounds are known to be active at the blood stage of the parasites but not at the hepatic stage.

Some of the known chemical compounds to treat malaria are not free of side effects, this rendering their long-term use deleterious in some aspects and limiting the use of these compounds.

There is therefore still a need for compounds having an efficiency against malaria, without their usual drawbacks, and not only at the blood stage but also at the hepatic stage, this conferring to the compounds a prophylactic effect. Furthermore, there is a need for anti-malarial drugs which are easy to formulate in pharmaceutical compositions.

The applicants have now found that some compounds isolated from Strychnopsis thouarsii and also synthetic derivatives thereof have good anti-malarial activity, particularly on the hepatic stage (also call exoerythrocytic stage) of Plasmodium, contrary to most of conventional antimalarial drugs which are only active on the erythrocytic cycle.

JP 62-263158 describes sinoccoculine as an anti-tumoral active agent and JP 62-289 565 describes tetracyclic alkaloids and their anti-tumoral activity, the compounds being extracted from Cocculus sarmentosus or Cocculus trilobus.

The present invention thus concerns the use of the compounds of formula I or II below and their derivatives as medicaments, particularly as anti-malarial compounds.

Amongst them, most are new. In another aspect, the invention concerns chemical compounds having the formula

wherein

-   -   R₁ is H or OC_(i)H_(2i+1) with i between 0 and 6;     -   R₂ is H or OC_(j)H_(2j+1) with j between 0 and 6;     -   R₃ is H or OC_(k)H_(2k+1) with k between 0 and 6;     -   R₄ is H or OH;     -   R₅ is OH or OC_(m)H_(2m+1) with m between 1 and 6 or an acetoxy         group or an oxo group;     -   R₆ is OH or OC_(n)H_(2n+1) with n between 1 and 6 or an acetoxy         group or an oxo group;     -   R₇ is OC_(p)H_(2p+1) with p between 0 and 6;     -   R₈ and R₉ may be similar or different and represent H or         OC_(q)H_(2q+1) with q between 0 and 6, or Hal where Hal is Cl,         Br, F or I, or form together a covalent bond whereby the bond is         a double bond or form with an oxygen atom an ether bond (epoxy         group);     -   R₁₀ is H or C_(r)H_(2r+1) with r between 1 and 12 or an         unsaturated alkyl group or a cycloalkyl group (tri- to hexa-)         unsaturated or not, with or without heteroatoms; or an aromatic         or a polycyclic aromatic group with or without heteroatoms; or         C_(s)H_(2s)-A with s between 1 and 12 and whereby A is a         saturated or (tri- to hexa-) unsaturated cycloalkyl group, with         or without heteroatoms or an aromatic or a polycyclic aromatic         group with or without heteroatoms or A is C₆H_(5−t)-(Hal)_(t)         with t between 1 to 5 or C₆H_(5−u)—(O—C_(v)H_(2v+1))_(u) with u         between 1 to 5 and v between 0 and 6; or R₁₀ represents two         substituents similar or different rendering the nitrogen atom         quaternized, or an oxygen atom (nitrone group) and in which case         the bond between the nitrogen atom and C₉ is a double bond; or         R₁₀ represents CH₂CH₂[OCH₂CH₂]_(w)OCH₂CH₂—B with w between 0 and         10 and where B is OH, O-D or NH-D where D is a C₁-C₁₂ alkyl         group bearing an electrophilic function such as an         isothiocyanate;     -   R₁₁ is H or OH or OC_(x)H_(2x+1) with x between 1 and 6 or Hal         where Hal is Cl, Br, F or I; or an acetoxy group or a sulfonate         ester group or an oxo group;     -   or R₁₀ and R₁₁ may represent an isoalkylidene group;         or

wherein R₁, R₂, R₃, R₅, R₆, R₇, R₈ and R₉ are defined as above,

-   -   R₄ is H or OH or OC_(l)H_(2l+1) with l between 2 and 6;     -   R₁₀ is C_(y)H_(2y) with y between 1 and 12 or         CH₂CH₂[OCH₂CH₂]_(z)OCH₂CH₂ with z between 0 and 10; and

-   R₁₁ is H or OH or OC_(x)H_(2x+1) with x between 1 and 6 or Hal where     Hal is Cl, Br, F or I; or an acetoxy group or a sulfonate ester     group or an oxo group;

-   and all stereoisomers and optical isomers thereof,

-   with the proviso that in formula (I) (1) R₂ is not H or alcoxy when     R₃ is OH or alcoxy and R₄ is H or OH and R₅ and R₆ are OH or acyloxy     and R₇ is OCH₃ and R₈ and R₉ represent a double bound and R₁ is H;     and (2) R₁ is not H when R₂ is H and R₃ and R₇ are OCH₃, R₄, R₅ and     R₆ are OH and R₈ and R₉ represent a double bound and R₁₀ is H, and     particularly with the proviso that in formula (I) (1) R₂ is not H or     alcoxy when R₃ is OH or alcoxy and R₄ is H or OH and R₅ and R₆ are     OH or acyloxy and R₇ is OCH₃ and R₈ and R₉ represent a double bound     and R₁, R₁₀ and R₁₁ are H; and (2) R₁ is not H when R₂ is H and R₃     and R₇ are OCH₃, R₄, R₅ and R₆ are OH and R₈ and R₉ represent a     double bound and R₁₀ and R₁₁ are H, which are known from JP     62-263158 and JP 62-289565.

In the following, the proviso is defined in that, in the compounds of formula I, (1) R₂ is not H or alcoxy when R₃ is OH or alcoxy and R₄ is H or OH and R₅ and R₆ are OH or acyloxy and R₇ is OCH₃ and R₈ and R₉ represent a double bound and R₁ is H; and (2) R₁ is not H when R₂ is H and R₃ and R₇ are OCH₃, R₄, R₅ and R₆ are OH and R₈ and R₉ represent a double bound and R₁₀ is H, but also in that in formula (I) (1) R₂ is not H or alcoxy when R₃ is OH or alcoxy and R₄ is H or OH and R₅ and R₆ are OH or acyloxy and R₇ is OCH₃ and R₈ and R₉ represent a double bound and R₁, R₁₀ and R₁₁ are H; and (2) R₁ is not H when R₂ is H and R₃ and R₇ are OCH₃, R₄, R₅ and R₆ are OH and R₈ and R₉ represent a double bound and R₁₀ and R₁₁ are H.

Particularly, the invention concerns the compounds of formula I with the above proviso and the use of compounds of formula I without the proviso for their antimalarial activity. Amongst them, the preferred compounds are those wherein R₈ and R₉ form a double bound, and R₁ and R₂ are H, and particularly the compounds wherein R₁₁ is OH.

According to an aspect of the invention, R₁₀ can represent H or C_(r)H_(2r)-A with r between 1 and 12 and whereby A is H or a cycle C_(s)H_(2s−1) with s between 3 and 6 or an aromatic cycle or an aromatic polycycle or an aromatic cycle substituted as C₆H_(5−t)-(Hal)_(t) with t between 1 to 5 and where Hal is Cl, Br, F or I, or as C₆H_(5−u)—(O—C_(v)H_(2v+1))_(u) with u between 1 to 5 and v between 0 to 6, or as C₆H_(5−w)—(NH₂)_(w) with w between 1 to 2; or R₁₀ represents two substituents similar or different rendering the nitrogen atom quaternized, or an oxygen atom; or R₁₀ represents CH₂—CH₂—[O—CH₂—CH₂]_(x)O—CH₂—CH₂—B with x between 0 and 10 and whereby B is H or OH or NH₂ or N═C═S.

The preferred compounds are described hereafter namely in the examples and the detailed description.

More particularly, the invention thus concerns 4,6,7,10-tetrahydroxy-8,14-didehydro-3,8-dimethoxymorphinan and its derivative N-methyl-, N-propyl-, N-4-methoxybenzyl-, N4-hydroxybenzyl-, N-4-bromobenzyl- or N-cyclopentyl-4,6,7,10-tetrahydroxy-8,14-didehydro-3,8-dimethoxy-morphinan, as well as their pharmaceutically acceptable salts, and their optical isomers including racemates, and more particularly the isomers having the optical configuration (6S, 7S, 9R, 10R, 13S).

More particularly, the invention concerns

and the use of (2)

as anti-malarial compounds.

Furthermore, the invention concerns pharmaceutical compositions containing the compounds of formula I or II as above defined and stereoisomers and optical isomers and pharmaceutically acceptable salts thereof as an active agent together with an pharmaceutically acceptable vehicle, particularly an aqueous vehicle.

It also concerns pharmaceutical compositions comprising a compound of formula I or formula II as above defined, without the proviso together with at least one second anti-malarial compound and a pharmaceutically acceptable vehicle.

It also concerns the use of these compounds for the preparation of a pharmaceutical composition useful in the treatment of malaria, said composition comprises at least a compound of formula I or II without the proviso and another anti-malarial compound.

The invention further concerns the use of the compounds of formula I or II without the proviso and all the stereoisomers and optical isomers thereof, for the preparation of a pharmaceutical composition useful in the prophylactic or curative treatment of malaria.

According to a further aspect, the invention concerns pharmaceutical compositions comprising an isolated extract of Strychnopsis thouarsii having an anti-malarial activity.

It also concerns pharmaceutical compositions comprising an isolated extract of Strychnopsis thouarsii and at least a compound of formula I or II and a pharmaceutically acceptable vehicle.

The invention also concerns the use of an isolated extract of Strychnopsis thouarsii in the preparation of a pharmaceutical composition comprising at least said extract of Strychnopsis thouarsii and a pharmaceutically acceptable vehicle, the composition being useful in a prophylactic or curative treatment of the malaria.

The compounds of the invention have an anti-malaria activity particularly drawn to the hepatic stage, which corresponds to the passage of the parasite into the liver and to the infection of the hepatic cells in which the parasites develop to form the hepatic schizonts which, when they are mature (for example in the case of P. falciparum on the 6^(th) day after penetration of the sporozoites) release hepatic merozoites by bursting. The third stage is characterized by the infection of the blood erythrocytes by the asexual forms (merozoites) of the parasite; this erythrocytic stage of development corresponds to the pathogenic phase of the disease. The fourth stage corresponds to the formation of the forms with sexual potential (or gametocytes) which will become extracellular sexual forms or gametes in the mosquito. The second stage is also called the exoerythrocytic stage of Plasmodium.

The only known and practically used molecules that are active against the hepatic stage are primaquine and atovaquone.

Their use is however limited due to the very toxic nature of primaquine, and due to the rapid development of resistance for atovaquone which is therefore only used in combination with other anti-malarial drugs.

The compounds of the invention are particularly useful for prophylactic and curative treatment of the hepatic stage of malaria. Furthermore, the compounds of the present invention are shown to kill parasites just after transmission by the infected mosquitoes and before it becomes pathogenic by multiplication in the red blood cells. The invention compounds are therefore especially useful for antimalarial prophylaxis particularly as compared with the usual treatments.

Decoction and methanolic extract of the plant were evaluated for their in vitro antimalarial activity through inhibition of Plasmodium growth in murine and human hepatocytes, according to tests as described below.

A bioassay-guided fractionation of the plant extract, linking this in vitro test to chromatographic separation techniques was carried out and led to the isolation of active compounds, as described below.

The invention therefore also encompasses isolated extracts of bark or leaves of the plants described therein for use in a pharmaceutical compositions.

The pharmaceutical compositions of the present invention contain a pharmaceutically acceptable carrier in addition to the invention compound(s). The pharmaceutically acceptable carrier depends on the dosage form.

One of the advantages of the invention compounds is their bio-availability. Their solubility in water and aqueous vehicles is a major advantage.

Amongst the pharmaceutically acceptable vehicle, aqueous vehicle are preferred.

When the pharmaceutical compositions are used for oral administration, they may appropriately contain pharmaceutically acceptable carriers including binders such as dicalcium phosphate; disintegrants such as sucrose; dyes; and perfumes such as orange flavor; and solvents such as water, ethanol and glycerol.

When pharmaceutical compositions of the present invention are injectable compositions, suitable pharmaceutically acceptable carriers include sterilized water, isotonic saline and pH buffers. Alternatively, injectable compositions of the present invention may be sterilized powder compositions or lyophilized powder compositions that can be used by simple dissolution in sterilized water. Injectable pharmaceutical compositions of the present invention may contain sugars (glucose, mannitol and dextran, etc.), polyhydric alcohols (glycerol, etc.), and inorganic salts (sodium salts and magnesium salts, etc.).

When pharmaceutical compositions of the present invention are administered by intravenous injection or infusion, they may contain nutrients such as glucose, vitamins, amino acids and lipids.

Pharmaceutical carriers to be added to dosage forms for other administration modes such as nasal administration, inhalation and transdermal administration are also well-known to those skilled in the art.

When pharmaceutical compositions of the present invention are orally administered, they may be in the form of controlled- or sustained-release formulations. Well-known sustained-release formulations include ordinary sustained- or controlled-release formulations such as gel-coated formulations and multicoated formulations as well as site-specific delivery formulations (e.g., burst release at pyloric regions or effervescent delivery to the duodenum). Oral compositions include, for example, tablets, pills, capsules, ampoules, sachet, elixir, suspensions, syrups, etc.

The dosage forms and pharmaceutical carriers mentioned above are described in Remington's Pharmaceutical Sciences, 16^(th) ed. (1980), Mack Publishing Company, which is incorporated herein by reference.

Pharmaceutical compositions or unit dose systems of the present invention can be administered via various other routes such as transmucosal (sublingual, nasal, buccal), enteral, dermal administration, suppositories or intravenous infusion. These administration modes depend on the amount of the active compound to be administered, the condition of the patient and other factors.

Among these administration modes, oral administration is especially preferred as well as any mode where the use of aqueous vehicle is of interest.

According to the invention the inventive compound is present in an amount of between 0.001 and 50% by weight of the pharmaceutical composition.

When present in combination with a second anti-malarial compound or as an enhancer of the anti-malarial activity of another anti-malarial compound, the inventive compound is present in an amount between 0.0001 and 20% by weight of the pharmaceutical composition.

In the present invention, the effective amount of inventive compound used for the treatment of malaria is normally 1-1,000 mg/kg weight daily, preferably 5-500 mg/kg weight daily depending on the age, body weight and condition of the patient and the administration mode.

Apart from their obtention by the extraction process, the compounds of the invention can be obtained by synthesis. As it appears from the following examples, the derivatives of (1) and (2) can be prepared according to usual chemical procedures. Particularly alkylation procedures are carried out on products (1) and (2) under suitable alkylation conditions with the corresponding suitable alkylating agents. For example suitable alkylating agents are the corresponding aldehydes or dialdehydes. Suitable conditions can be reductive alkylation conditions.

Furthermore, oxidation and subsequent alkylation can be carried out by usual procedures, and protection of the substituants previously performed, if necessary.

In the following examples, stem bark has been treated to extract the compounds from the plant. However, other parts of the plant might be treated, as well as other species able to produce similar extracts. The leaves of Strychopsis thouarsii can also be used, as well as other plants and species. The person skilled in the art can adapt the separation process to the species or part of the plant to be treated.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph indicating the percentage parasitemia days post-infection. The control group is indicated by an •, while the treated group with compound (1) is indicated with ⋄.

PREPARATION EXAMPLES Example 1 Extraction Process

500 g powdered Strychnopsis thouarsii stem bark was soaked under stirring in MeOH at room temperature for six days, according to the following procedure.

Each 24 hours, the solute was filtrated and the solid residue was treated with 2 l MeOH. The resulting six solutes were pooled and evaporated to dryness under reduced pressure, providing 22 g of methanolic extract.

This extract was dissolved in 2 l H₂O and centrifugated at 10,000 rpm for 1 hour. A residue of 10 g was removed, while the supernatant was partitioned three times between H₂O and CH₂Cl₂ (500 mL).

The resulting aqueous extract of 11.7 g was chromatographed on a reversed phase silica gel column (RP-2), eluted with a discontinuous gradient of H₂O-MeOH in the proportion of (100-0, 90-10, 80-20, 0-100).

The fractions were pooled according to their TLC profiles into 3 fractions F1 to F3.

The fraction F1 (9.4 g) was further separated on a silica gel column, eluted with CH₂Cl₂-MeOH—NH₄OH (85-15-0.5) leading to 10 fractions F1-1 to F1-10.

The fraction F1-6 was determined to be the most active amongst the obtained fraction, by an evaluation of the biological activity carried out according to the method as described below.

Example 2 Isolation of Compounds (1) and (2)

Compound (1)=4,6,7,10-tetrahydroxy-8,14-didehydro-3,8-dimethoxy-morphinan C₁₈H₂₃NO₆

Compound (2)=4,6,7-trihydroxy-8,14-didehydro-3,8-dimethoxy-morphinan (Sinococuline or FK1000) [CAS Registry Number: 109351-36-2] C₁₈H₂₃NO₅

An aliquot of fraction F1-6 (0.850 g) was chromatographed on a sephadex gel column (LH-20) eluted with MeOH, leading to 4 fractions, F1-6-1 to F1-6-4.

The fraction F1-6-3 (0.368 g) was purified on a silica gel column eluted with CH₂Cl₂-MeOH—NH₄OH (87-13-1), leading to 6 fractions, F1-6-3-1 to F1-6-3-6.

The fraction F1-6-3-4 (0.122 g) was shown to be a mixture of the two compounds (1) and (2).

An aliquot of F1-6-3-4 (0.045 g) was further submitted to a preparative silica gel TLC migrating in CHCl₃—NH(C₂H₅)₂ (70-30), leading to 2 fractions, F1-6-3-4-1 (0.01 g) and F1-6-3-4-2 (0.028 g).

The first fraction was submitted to a silica gel column filtration with CH₂Cl₂-MeOH—NH₄OH (70-30-3), providing pure compound (2) (0.004 g), while the second fraction, under the same conditions, afforded pure compound (1) (0.019 g).

Example 3 Isolation of Compounds (1) and (2)

An aliquot of fraction F1-6 (0.22 g) was straightly subjected to a preparative silica gel TLC migrating in CHCl₃-MeOH—NH₄OH (75-25-3.5), providing compound (1) (0.04 g), while bands corresponding to less polar products were pooled and submitted to a second preparative TLC migrating in CHCl₃-MeOH—CH₃COOH—H₂O (75-18-4-3), leading to 3 fractions, F1-6-1′ to F1-6-3′.

The fraction F1-6-1′ (0.012 g) was subjected to a silica gel column filtration with CH₂Cl₂-MeOH—NH₄OH (90-10-1), providing pure compound (2) (0.004 g).

Example 4 Analytical Data of Compounds (1) and (2)

1) Compound (1)

a) NMR data of (1) in CD₃OD and its attribution by 2D NMR (400 MHz):

Carbon number δ H (multiplicity, J in Hz) δ C  1 6.86 (d, 8.4) 121.93  2 6.90 (d, 8.4) 110.67  3 — 149.18  4 — 145.07  5 ₁ 2.95 (dd, 3.3, 13.4) 36.51  5 ₂ 2.19 (dd, 13.4, 13.4)  6 3.86 (m, 2.7, 3.3, 13.4) 68.60  7 4.28 (d, 2.7) 66.91  8 — 148.49  9 4.33 (d, 2.2) 53.13 10 4.53 (d, 2.2) 73.31 11 — 132.91 12 — 129.78 13 — 40.05 14 — 121.09 15 ₁ 1.99 (dd, 3.6, 12.5) 37.50 15 ₂ 1.84 (ddd, 4.7, 12.5, 12.5) 16 ₁ 2.64 (dd, 4.7, 14.3) 40.85 16 ₂ 2.42 (ddd, 3.6, 14.3) 3-OCH₃ 3.86 (s) 56.57 8-OCH₃ 3.69 (s) 57.06

b) Physico-chemical data of (1)

Mass Spectroscopy (ESI-TOF⁺): m/z 350.1 [M+H]⁺

Mass calculated for C₁₈H₂₄NO₆: 350.1604

High Resolution MS (DCI⁺): m/z 350.1604 [M+H]⁺

UV (λ_(max)nm (ε), MeOH): 282 (3318), 242_(sh) (9926), 207 (57483)

[α]²⁰ _(D) −46° (c 0.5, MeOH)

Circular Dichroism (λext_(nm), θ): (216, +66324), (227, −15949), (242, +16864)

(c=1.15×10⁻³ M, MeOH)

2) Compound (2)

a) NMR data of (2)

¹H-NMR (300 MHz, CD₃OD): δ 6.85 (d, 1H, J=8.3 Hz), 6.62 (dd, 1H, J=1.2, 8.3 Hz), 4.96 (dd, 1H, J=1.7, 6.2 Hz), 4.39 (dd, 1H, J=1.1, 3.1 Hz), 3.87 (ddd, 1H, J=3.1, 3.9, 13.5 Hz), 3.84 (s, 3H), 3.78 (s, 3H), 3.31 (ddd, 3H, J=1.2, 6.2, 19.1 Hz), 3.14 (dd, 1H, J=4.6, 13.1 Hz), 3.10 (dd, 1H, J=1.7, 19.1 Hz), 3.03 (ddd, 1H, J=1.1, 3.9, 13.5 Hz), 2.84 (ddd, 1H, J=4.1, 13.1, 13.2 Hz), 2.24 (dd, 1H, J=13.5, 13.5 Hz), 2.19 (dd, 1H, J=4.1, 13.2 Hz), 2.06 (ddd, 1H, J=4.6, 13.2, 13.2 Hz)

¹³C-NMR (300 MHz, CD₃OD): δ 33.53, 34.08, 36.0, 38.46, 40.67, 47.96, 56.22, 56.67, 65.38, 68.11, 111.30, 113.92, 119.48, 127.90, 128.56, 145.79, 148.09, 150.66

The NMR data of (2) were similar to those previously described in literature [1, 2].

b) Physico-chemical data of (2)

Mass Spectroscopy (ESI-TOF⁺): m/z 334.1 [M+H]⁺

Mass calculated for C₁₈H₂₄NO₅: 334.1654

High Resolution MS calculated for C₁₈H₂₃NO₅: 334.1655

UV (MeOH) λ_(max)nm (ε): 282 (2856), 242_(sh) (6984), 207 (59602)

[α]²⁰ _(D) −143° (c 0.25, MeOH) cf. [3] [α]²⁰ _(D) −137.4° (c 0.12, MeOH)

Circular Dichroism (λext_(nm), θ): (216, +63340), (227, −15231), (242, +16105)

(c=1.20×10⁻³ M, MeOH)

cf. [1] CD (λext_(nm), θ): (238, +62100) (c=9.67×10⁻⁵ M, MeOH)

3) Stereochemistry of Compounds (1) and (2):

Specific rotation values of compound (2) and sinococuline were closely the same.

Compounds (1) and (2) showed the same Nuclear Overhauser Effect SpectroscopY (NOESY) correlations (cf. table 1) as sinococuline. Consequently compounds (1) and (2) have been assigned with the same relative configuration (6S*, 7S*, 9R*, 13S*) as sinococuline.

Moreover, compounds (1) and (2) exhibited similar CD spectra (positive maxima at 216 nm and 242 nm, negative maximum at 227 nm), in agreement with this of sinococuline described in literature, allowing us to conclude that the absolute configuration of compound (1) and compound (2) is (6S, 7S, 9R, 10R, 13S) and (6S, 7S, 9R, 13S) respectively.

TABLE 1 NOESY (2D-NMR, 400 MHz, MeOH) Compound (1) Compound (2) Proton n° Correlated protons Correlated protons  1 H10 H2, H10₁, H10₂  2 3-OCH₃ H1, 3-OCH₃  3 — —  4 — —  5 ₁ H15₁, H5₂, H6, H7 H5₂, H6  5 ₂ H5₁, H6 H5₁, H6  6 H15₂, H5₂, H5₁, H7 H5_(1,) H5₂, H7, H15₂  7 8-OCH₃, H6 3-OCH₃, H5₂, 8-OCH₃  8 — —  9 8-OCH₃, H10 8-OCH₃, H10₁, H10₂ 10 ₁ H16₂, H9, H1 H1, H9, H10₂ 10 ₂ H1, H9, H10₁ 11 — — 12 — — 13 — — 14 — — 15 ₁ H15₂, H16₂, H16₁, H5₁ H5₁, H15₂, H16₂ 15 ₂ H15₁, H16₁, H6 H6, H15₁, H16₁ 16 ₁ H15₁, H15₂, H16₂ H15₁, H15₂, H16₂ 16 ₂ H15₁, H16₁, H10 H15₁, H16₁ 3-OCH₃ H2 H2 8-OCH₃ H7, H9 H7

Example 5 N-methyl-4,6,7,10-tetrahydroxy-8,14, didehydro-3,8-dimethoxy-morphinan (3) C₁₉H₂₅NO₆

1) Preparation of Compound (3)

To a solution of (1) (10.9 mg, 0.031 mmol) in 1 mL MeOH was added 100 μl of a solution of formaldehyde (37% in water). After stirring for 1 hour at room temperature, 3 mg of NaBH₄ was added and the mixture was stirred for additional 3 hours.

After removal of the solvent under reduced pressure, the residue was acidified with 1N HCl, then basified with 20% aqueous NH₄OH and was further submitted to a silica gel column eluted with CH₂Cl₂-MeOH—NH₄OH (85-15-1), leading to compound (3) as a white solid (8 mg, 0.022 mmol), 71% yield.

2) Analytical Data of (3)

¹H-NMR (300 MHz, CD₃OD): δ 6.90 (d, 1H, J=8.4 Hz), 6.83 (d, 1H, J=8.4 Hz), 4.70 (d, 1H, J=2.2 Hz), 4.30 (dd, 1H, J=1.3, 3.4 Hz), 4.21 (d, 1H, J=2.2 Hz), 3.88 (m, 1H, J=3.4, 4.1, 13.8 Hz), 3.87 (s, 3H), 3.70 (s, 3H), 2.98 (ddd, 1H, J=1.3, 4.1, 13.8 Hz), 2.51 (dd, 1H, J=3.3, 12.4 Hz), 2.47 (s, 3H), 2.26 (m, 1H, J=2.9, 12.4, 12.9 Hz), 2.18 (dd, 1H, J=13.8, 13.8 Hz), 1.95 (m, 2H, J=2.9, 3.3, 12.9 Hz)

Mass Spectroscopy (ESI-TOF⁺): m/z 364.1 [M+H]⁺

Mass calculated for C₁₉H₂₆NO₆: 364.1760

High Resolution MS (DCI⁺): m/z 364.1764 [M+H]⁺

[α]²⁰ _(D) −41° (c 0.5, MeOH)

Example 6 N-propyl-4,6,7,10-tetrahydroxy-8,14, didehydro-3,8-dimethoxy-morphinan (4) C₂₁H₂₉NO₆

1) Preparation of Compound (4)

To a solution of (1) (3.05 mg, 0.0087 mmol) in 300 μl MeOH, was added 1 μl, 0.014 mmol of propionaldehyde and 0.6 mg, 0.0095 mmol of sodium cyanoborohydride NaBH₃CN. The mixture was stirring for 4 hours at room temperature.

After removal of the solvent under reduced pressure, the residue was acidified with HCl 1N, then basified with 20% aqueous NH₄OH and was submitted to a preparative TLC eluted twice with CH₂Cl₂-MeOH—NH₄OH (90-10-1) to provide (4) as a white solid (2.3 mg, 0.0059 mmol), 68% yield.

2) Analytical Data of (4)

¹H-NMR (300 MHz, CD₃OD): δ 6.99 (d, 1H, J=8.4 Hz), 6.96 (d, 1H, J=8.4 Hz), 4.82 (d, 1H, J=1.9 Hz), 4.72 (s, 1H), 4.37 (d, 1H, J=3.3 Hz), 3.92 (m, 1H), 3.89 (s, 3H), 3.78 (s, 3H), 3.05 (m, 4H), 2.66 (m, 2H), 2.27 (dd, 1H, J=13.5, 13.5 Hz), 2.11 (dd, 1H, J=3.9, 12.3 Hz), 1.77 (m, 2H, J=2.2, 7.3, 7.3 Hz), 1.02 (t, 3H, J=7.3 Hz)

Mass Spectroscopy (ESI-TOF⁺): m/z 392.2 [M+H]⁺

Mass calculated for C₂₁H₃₀NO₆: 392.2073

High Resolution MS (DCI⁺): m/z 392.2064 [M+H]⁺

[α]²⁰ _(D) −18° (c 0.1 MeOH)

Example 7 N-4-methoxybenzyl-4,6,7,10-tetrahydroxy-8,14, didehydro-3,8-dimethoxy-morphinan (5) C₂₆H₃₁NO₇

1) Preparation of Compound (5):

To a solution of (1) (5.7 mg, 0.016 mmol) in 500 μl MeOH, was added 200 μl, 1.6 mmol of anisaldehyde. After stirring for 1 hour at room temperature, 3 mg of NaBH₄ was added and the mixture was stirred for additional 3 hours at room temperature.

After removal of the solvent under reduced pressure, the residue was acidified with HCl 1 N, then basified with 20% aqueous NH₄OH and was submitted to a preparative TLC, eluted twice with CH₂Cl₂-MeOH—NH₄OH (90-10-1.5) to provide (5) as a white solid (3.0 mg, 0.0064 mmol), 40% yield.

2) Analytical Data of (5)

¹H-NMR (300 MHz, CD₃OD): δ 7.47 (d, 2H, J=8.6 Hz), 7.0 (d, 2H, J=8.6 Hz), 6.98 (d, 1H, J=8.4 Hz), 6.93 (d, 1H, J=8.4 Hz), 4.88 (s, 1H), 4.71 (s, 1H), 4.40 (d, 1H, J=2.8 Hz), 4.25 (s, 2H), 3.99 (m, 1H), 3.88 (s, 3H), 3.83 (s, 3H), 3.77 (s, 3H), 3.06 (m, 2H, J=3.6, 3.9, 12.5, 13.6 Hz), 2.75 (dd, 1H, J=2.1, 12.5 Hz), 2.28 (ddd, 1H, J=3.2, 13.6, 13.6 Hz), 2.20 (dd, 1H, J=3.9, 13.2 Hz), 2.07 (dd, 1H, J=2.1, 13.2 Hz)

MS (ESI-TOF⁺): m/z 470.2 [M+H]⁺

Mass calculated for C₂₆H₃₂NO₇: 470.2179

High Resolution MS (DCI⁺): m/z 470.2170 [M+H]⁺

[α]²⁰ _(D) −12° (c 0.1, MeOH)

Example 8 N-4-hydroxybenzyl-4,6,7,10-tetrahydroxy-8,14, didehydro-3,8-dimethoxy-morphinan (6) C₂₅H₂₉NO₇

1) Preparation of Compound (6)

To a solution of (1) (4.85 mg, 0.014 mmol) in 500 μl of MeOH was added 4-hydroxy-benzaldehyde (1.7 mg, 1 eq). After stirring for 4 hours at room temperature, 0.9 mg, 1 eq of NaBH₃CN was added and the mixture was stirred for additional 3 hours at room temperature.

After removal of the solvent under reduced pressure, the residue was acidified with HCl 1N, then basified with 20% aqueous NH₄OH and was submitted to a preparative TLC, eluted twice with CH₂Cl₂-MeOH—NH₄OH (90-10-1) to provide (6) as a white solid (3.5 mg, 0.0077 mmol), 55% yield.

2) Analytical Data of (6)

¹H-NMR (300 MHz, CD₃OD): δ 7.29 (d, 2H, J=8.6 Hz), 6.96 (d, 1H, J=8.4 Hz), 6.91 (d, 1H, J=8.4 Hz), 6.82 (d, 2H, J=8.6 Hz), 4.79 (s, 1H), 4.57 (d, 1H, J=1.6 Hz), 4.37 (d, 1H, J=3.3 Hz), 4.01 (d, 2H, J=8.1 Hz), 3.94 (ddd, 1H, J=3.7, 3.7, 12.9 Hz), 3.87 (s, 3H), 3.72 (s, 3H), 3.02 (dd, 1H, J=4.1, 13.5 Hz), 2.88 (d, 1H, J=12.6 Hz), 2.59 (ddd, 1H, J=3.7, 12.6, 12.6 Hz), 2.25 (dd, 1H, J=13.5, 13.5 Hz), 2.12 (ddd, 1H, J=4.5, 12.6, 12.6 Hz), 2.01 (d, 1H, J=12.6 Hz)

Mass Spectroscopy (ESI-TOF⁺): m/z 456.2 [M+H]⁺

Mass calculated for C₂₅H₃₀NO₇: 456.2022

High Resolution MS (DCI+): m/z 456.2018 [M+H]⁺

[α]²⁰ _(D) −10° (c 0.03, MeOH)

Example 9 N-4-bromobenzyl-4,6,7,10-tetrahydroxy-8,14, didehydro-3,8-dimethoxy-morphinan (7) C₂₅H₂₈NO₆Br

1) Preparation of Compound (7)

To a solution of (1) (3.3 mg, 0.0095 mmol) in 300 μl MeOH was added 2 mg, 0.011 mmol of 4-bromo-benzaldehyde and 3 mg of NaBH₃CN. The mixture was stirred 20 hours at room temperature.

After removal of the solvent under reduced pressure, the residue was acidified with HCl 1N, then basified with 20% aqueous NH₄OH and was submitted to a preparative TLC eluted twice with CH₂Cl₂-MeOH—NH₄OH (95-5-0.5) to provide (7) as a white solid (3.0 mg, 0.0058 mmol), 61% yield.

2) Analytical Data of (7)

¹H-NMR (300 MHz, CD₃OD): δ 7.51 (d, 2H, J=8.4 Hz), 7.35 (d, 2H, J=8.4 Hz), 6.92 (d, 1H, J=8.4 Hz), 6.88 (d, 1H, J=8.4 Hz), 4.78 (d, 1H, J=3.4 Hz), 4.74 (s, 2H), 4.73 (d, 1H, J=2.2 Hz), 4.32 (d, 1H, J=1, 3.4 Hz), 3.93 (ddd, 1H, J=2.9, 3.4, 13.5 Hz), 3.88 (s, 3H), 3.68 (s, 3H), 3.0 (dd, 1H, J=2.9, 13.5 Hz), 2.66 (m, 1H, J=4.6, 12.1 Hz), 2.46 (ddd, 1H, J=3.9, 12.1, 12.1 Hz), 2.21 (dd, 1H, J=13.5, 13.5 Hz), 2.05 (ddd, 1H, J=4.6, 12.6, 12.6 Hz), 1.94 (ddd, 1H, J=1.9, 3.9, 12.6 Hz)

Mass Spectroscopy (ESI-TOF⁺): m/z 519.1 and 521.1 [M+H]⁺

Mass calculated for C₂₅H₂₉NO₆Br: 519.1035 and 521.1055

High Resolution MS (DCI⁺): m/z 519.1037 and 521.1058 [M+H]⁺

[α]²⁰ _(D) −0.5° (c 0.5, MeOH)

Example 10 N-cyclopentyl-4,6,7,10-tetrahydroxy-8,14, didehydro-3,8-dimethoxy-morphinan (8) C₂₃H₃₁NO₆

1) Preparation of Compound (8)

To a solution of (1) (4.95 mg, 0.014 mmol) in 300 μl of MeOH was added 2 μl, 0.023 mmol of cyclopentanone and 3 mg of NaBH₃CN. The mixture was stirred for 6 hours at room temperature.

After removal of the solvent under reduced pressure, the residue was acidified with 1 N HCl, then basified with 20% aqueous NH₄OH and was submitted to a preparative TLC eluted twice with CH₂Cl₂-MeOH—NH₄OH (90-10-1) to provide (8) as a white solid (4.75 mg, 0.011 mmol), 81% yield.

2) Analytical Data of (8)

¹H-NMR (300 MHz, CD₃OD): δ 6.98 (d, 1H, J=8.4 Hz), 6.94 (d, 1H, J=8.4 Hz), 4.83 (s, 1H), 4.71 (s, 1H), 4.37 (d, 1H, J=2.7 Hz), 3.91 (m, 1H), 3.88 (s, 3H), 3.78 (s, 3H), 3.21 (d, 1H, J=12.6 Hz), 3.05 (dd, 1H, J=3.5, 14.3 Hz), 2.27 (m, 2H, J=12.6, 14.3 Hz), 2.16 (m, 1H), 1.86 (m, 4H), 1.65 (m, 6H)

Mass Spectroscopy (ESI-TOF⁺): m/z 418.2 [M+H]⁺

Mass calculated for C₂₃H₃₂NO₆: 418.2230

High Resolution MS (DCI⁺): m/z 418.2239 [M+H]⁺

[α]²⁰ _(D) −30° (c 0.03, MeOH)

Evaluation of the Biological Activity of Compounds

Materials and Methods

In vitro Evaluation of the Antimalarial Activity of Plant Extracts and Pure Compounds (1)-(8)

A—Murine Model: Hepatic Stage of Plasmodium yoelii yoelii 265BY.

Primary cultures of mouse hepatocytes were isolated from livers of Swiss mice which were 6 to 8 weeks old by perfusion with collagenase (1 g/L) and purified through a 60% Percoll gradient.

The hepatocytes were cultured in sterile chambers (Lab-Tek) at the rate of 90,000 cells in 0.3 mL of complete culture medium as defined thereafter per well and incubated overnight at 37° C. under a 4% CO₂ atmosphere. The hepatocytes' complet culture medium was Williams' E culture medium supplemented with 10% of decomplemented foetal calf serum, 1% glutamine, 1% Na pyruvate, 1% of a mixture of insulin, transferrine and selenium, 1% of non-essential amino-acids and with an antibiotic mixture comprising 1% of a solution of penicillin and streptomycine, 1% augmentin and 2.5 pg/ml flucytosine.

The parasites infecting the hepatocytes; i.e. the sporozoites, were recovered by dissection of infected anopheles mosquitoes salivary glands.

After grinding them in a Potter grinder with culture medium, the suspension was filtered on a 40 μm mesh filter and centrifuged (15,000 rpm) at 4° C. for 2 mn. The pellet was reintroduced in the complete culture medium. The sporozoites were then counted in a “Cell Vu” counter (CML) and the concentration was adjusted at 100,000 sporozoites per 70 μL, concentration needed for infection.

One day after, the hepatocytes were infected by the above sporozoites from salivary glands of infected anopheles mosquitoes at the rate of 100,000 sporozoites per well in the presence or absence of the product to be tested. When the infection had appeared, the medium was supplemented with 10⁻⁷ M dexamethasone. The products were first solubilized in DMSO.

The infected hepatocytes were washed and fed with culture medium containing the test product, 3 hours and then 24 hours after the infection.

The cultures were stopped by treatment with a cold fixative methanol solution, 48 hours after the infection.

Parasites obtained in schizont stage were immunomarked firstly, with a serum isolated from BALB/c mice immunized with a recombinant fragment from the N-terminal of the recombinant protein I72 that reacted against HSP70 of Plasmodium [4] and secondly with an antibody—a mouse anti-immunoglobulin—conjugated to FITC. Evans Blue and DAPI, a nucleic acid marker, were added to the hepatocytes simultaneously. The schizonts were then counted with a fluorescent microscope.

Extracts and purified products exhibiting a significant inhibition effect on P. yoelii yoelii 265BY growth in murine hepatocytes were tested on human hepatocyte cultures infected with P. falciparum NF54.

B—Human Model: Hepatic Stage of Plasmodium falciparum NF54

Human hepatocytes were obtained by enzymatic perfusion of fragments of liver of human adults which were submitted to partial hepatectomy.

The hepatocytes were infected at 24 hours of their culture by sporozoites obtained from salivary glands of P. falciparum infecting anopheles mosquitoes stephensi (Lab. of Pr. W. Eling, Univ. Of Nijmegen, NL).

The culture medium containing the test product was changed 3 hours after infection, and then renewed at least, each 24 hours during the experiment.

The cultures were fixed 5 days after infection, with the same method as described for the murine hepatocytes [5].

The Cl₅₀ value (concentration causing 50% of inhibition in the number of parasites compared to controls wells, non treated) is the mean value of 3 independent evaluations through StatView SI Graphics.

In vitro Evaluation of the Cytotoxicity of Plant Extracts and Pure Compounds (1)-(8)

The cytotoxicity assays were carried out in 96-well microliter plates, in triplicate, against human carcinoma KB cell line (ATCC CCL-17) (10⁴ cells/mL in DMEM medium) and human colon tumor HT29 cell line (ATCC HTB-38) (10⁵ cells/mL in RPMI 1640 medium), both supplemented with 10% foetal calf serum, L-glutamine (2 mM), penicillin G (100 UI/mL), streptomycin (100 μg/mM) and gentamycin (10 μg/mL).

Stock solutions of testing compounds were prepared in H₂O/DMSO (9/1).

After an incubation of 72 hours at 37° C. under a 5% CO₂ atmosphere, 0.02% of neutral red in PBS was added.

24 hours later, culture media were eliminated and cell membranes were lysed by addition of 1% of SDS in water.

Cell growth was estimated by colorimetric measurement of stained living cells, incorporating neutral red. Optical density was determined at 540 nm on a Titertek Multiskan photometer.

The Cl₅₀ value was defined as the concentration of compound necessary to inhibit the cell growth to 50% of the control.

Results

Table 2 represents in vitro activities of natural compounds (1) and (2) and N-substituted derivatives of (1), compounds (3)-(8), on growth inhibition of P. yoelii yoelii 265 BY in murine hepatocytes and their cytotoxicity on human tumor cell lines.

In Table 2, R represents the group introduced on the nitrogen atom by chemical modification of (1) as defined in formula I. The selectivity index (=ratio between Cl₅₀ of cytotoxicity and Cl₅₀ of anti-malarial activity) that was calculated, should the real effect of the compounds on Plasmodium parasites with respect to mammalian cells.

Primaquine and atovaquone were tested as references for their inhibiting activities on hepatic stage of Plasmodium, while 5-fluorouracile and vinblastine were tested as references for their cytotoxic activities on KB and HT29 cells.

TABLE 2 CI₅₀ activity Selectivity P. yoelii 265BY CI₅₀ cytotoxicity CI₅₀ cytotoxicity index Compound in μg/mL, KB HT29 CI₅₀ KB/CI₅₀ —R₁₀ (μM) in μg/mL, (μM) in μg/mL, (μM) yoelii (1) 1.08 1.99 ± 1.3 22.0 ± 12.5 1.8 —H [0.15-0.32]  5.7    63.0 3.1  (2) 1.50 1.30 ± 0.6 12.24 ± 8.59 0.9 —H [0.25-0.45  3.9    36.8 4.5  (3) 2.09 32.31 ± 7.1  >80 15.5 —CH3 [0.87-0.67] 89.0 >220 5.8  (4) 4.93 40.37 ± 13.9  >80 8.2 —CH2—CH2—CH3 [0.69-0.60] 103.2  >204 12.6 

11.4  [0.75-0.64] 24.2  21.23 ± 6.2 45.3  >80 >170 1.9

6.44 [0.92-0.80] 14.2  9.53 ± 3.3 20.9 48.96 ± 1.8   107.6 1.5

2.19 [0.92-0.71] 4.2  15.81 ± 6.4 30.5  >80 >154 7.3

1.46 [1.01-0.89] 3.5  27.64 ± 9.0  66.28  >80 >192 18.9 primaquine 0.16 2.0 ± 0.9 20.12 ± 2.1 11.7 [0.11-0.28]  7.0    70.51 0.6  Atovaquone  0.021 18.60 ± 8.7 44.60 ± 10.3 891.2 [0.003-.009] 50.8  122  0.057 5-fluorouracile / 0.047 ± 0.03 54.88 ± 2.4 /  0.36  422 Vinblastine / 0.018 ± 0.006 0.0080 ± 0.004 /   0.022      0.0099

Table 3 represents in vitro activities of natural compounds (1) and (2), on P. falciparum NF54 in human hepatocytes.

TABLE 3 CI₅₀ activity P. falciparum NF54 in μg/mL, (μM) (1) 1.51 [1.01-0.34] 4.3 (2) 3.36 [1.35-0.92] 10.1 

In vivo Evaluation of the Antimalarial Activity of Compound (1)

40 Swiss mice (six week old) have been subjected to the in vivo assay. They have been allotted in two groups:

-   -   a group of 20 mice were fed with compound (1) diluted in sterile         water at a dose of 100 mg/kg four times; 24 hours and 1 hour         before infection, 24 hours and 40 hours after infection during         the hepatic stage period.     -   a control group of 20 mice were fed with sterile water at the         same times.

The infection has been performed by retro-orbital injection of 4,000 sporozoites of Plasmodium yoelii yoelii 265BY in 100 μl phospate-buffered saline per mouse.

The parasitemia was monitored from the third day after the infection D3 when the parasites are liberated from the liver and enter into the blood circulation and each day until the 23rd day D23 after infection. The monitoring was performed by blood smears taken from the tail vein of the mice. The smears were stained with Giemsa and parasited red blood cells were counted with a microscope.

The parasitemia was calculated according to the following formula: Parasited red blood cell number×100/total red blood cell number.

Results

The following table presents the obtained results.

Number of parasited Days post-infection mice/20 total mice D3 D4 D5 D6 D7 D8 D23 Control Group 20/20 20/20 20/20 20/20 20/20 20/20 15/15 Treated group with  0/20  0/20  0/20  1/20  4/20  6/20  6/18 compound (1)

None of the treated mice were parasited at the fifth day after the infection whereas 100% of the control mice were parasited as soon as the third day.

In the treated group, the first mouse was parasited at the sixth day after infection with a delay of 3 days compared to the control group mice. At the end of the assay, on the 23^(rd) day, only 6 of the 20 treated mice were parasited, whereas 100% of the control mice were parasited. The results are set forth in FIG. 1.

As a first conclusion the treatment with compound (1) at 100 mg/kg allows a 70% total protection against malaria infection in mice, but also it allows a minimum 3 days delay for the 30% of treated mice, which were not protected.

As a second conclusion, the treatment with compound (1) at 100 mg/kg allows a better survival of mice at D23 in the treated group (90%) compared to the control group (75%).

Furthermore, the mean percentage of parasitemia was lower for mice parasited in the treated group compared to mice parasited in the control group (FIG. 1).

As a third conclusion, the treatment with compound (1) at 100 mg/kg allows a significant decrease of the number of parasited red blood cells.

The in vivo results confirm the in vitro results concerning the efficiency of compound (1) on the protection against Plasmodium yoelii 265BY and Plasmodium falciparum NF54. Compound (1) in oral administration, protects mice against infection by P. yoelii 265BY (70%), reduces parasitemia, delays apparition of the parasites and improves mice survival.

This prophylactic treatment differs from the usual treatments which mainly target the blood forms of the parasite.

REFERENCES

-   [1] Itokawa H., Tsuruoka S., Takeya K., Mori N., Sonobe T., Kosemura     S., Hamanaka T. An Antitumor Morphinane Alkaloid, Sinococuline, from     Cocculus trilobus. Chem. Pharm. Bull., 1987, 35, 1660-1662. -   [2] Deng J.-Z., Zhao S.-X., Miao Z.-C. A Morphinan Alkaloid from     roots of Stephania cepharantha. Phytochemistry, 1992, 31(4),     1448-1450. -   [3] Hitotsuyanagi Y., Nishimura K., Ikuta H., Takeya K., Itokawa H.     Synthesis of Antitumor morphinane Alkaloids, Sinococuline and     6-epi-, 7-epi-, and 6-epi-7-epi-Sinococuline, from Sinomenine. J.     Org. Chem., 1995, 60, 4549-4558. -   [4] Motard A., Marussig M., Renia L., Baccam D., Landau I., Mattei     D., Targett G., Mazier D. Immunization with the malaria heat shock     like protein hsp70-1 enhances transmission to the mosquito. Int.     Immunol., 1995, 7(1), 147-50. -   [5] Mazier D., Beaudoin R. L., Mellouk S., Druilhe P., Texier B.,     Trosper J., Miltgen F., Landau I., Paul C., Brandicourt O., et al.     Complete development of hepatic stages of Plasmodium falciparum in     vitro. Science, 1985, 227(4685), 440-2. 

1. A method for protecting against malaria infection in a subject or treating a subject suffering from malaria comprising: administering to said subject an effective amount of a compound of formula (I):

wherein R₁ is H or OC_(i)H_(2i+1) with i between 0 and 6; R₂ is H or OC_(j)H_(2j+1) with j between 0 and 6; R₃ is H or OC_(k)H_(2k+1) with k between 0 and 6; R₄ is H or OH; R₅ is OH or with OC_(m)H_(2m+1) between 1 and 6 or an acetoxy group or an oxo group; R₆ is OH or OC_(n)H_(2n+1) with n between 1 and 6 or an acetoxy group or an oxo group; R₇ is OC_(p)H_(2p+1) with p between 0 and 6; R₈ and R₉ may be similar or different and represent H or OC_(q)H_(2q+1) with q between 0 and 6, or Hal where Hal is Cl, Br, F or I, or form together a covalent bond whereby the bond is a double bond or an ether bond (epoxy group); R₁₀ is H or C_(r)H_(2r+1) with r between 1 and 12 or an unsaturated alkyl group or a cycloalkyl group (tri- to hexa-) unsaturated or not, with or without heteroatoms; or an aromatic or a polycyclic aromatic group with or without heteroatoms; or C_(s)H_(2s)-A with s between 1 and 12 and whereby A is a saturated or (tri- to hexa-) unsaturated cycloalkyl group, with or without heteroatoms or an aromatic or a polycyclic aromatic group with or without heteroatoms or A is C₆H_(5-t)-(Hal)_(t) with t between 1 to 5 or C₆H_(5-u)—(O—C_(v)H_(2v+1))_(u) with u between 1 to 5 and v between 0 and 6; or R₁₀ represents two substituents similar or different rendering the nitrogen atom quaternized, or an oxygen atom (nitrone group) and in which case the bond between the nitrogen atom and C₉ is a double bond; or R₁₀ represents CH₂CH₂[OCH₂CH₂]_(w)OCH₂CH₂—B with w between 0 and 10 and where B is OH, O-D or NH-D where D is a C₁-C₁₂ alkyl group bearing an electrophilic function such as an isothiocyanate; R₁₁ is H or OH or OC_(x)H_(2x+1) with x between 1 and 6 or Hal where Hal is Cl, Br, F or I; or an acetoxy group or a sulfonate ester group or an oxo group; or R₁₀ and R₁₁ may represent an isoalkylidene group; or a compound of formula (II):

wherein R₁, R₂, R₃, R₅, R₆, R₂, R₈ and R₉ are defined as above; R₄ is H or OH or OC_(l)H_(2l+1) with 1 between 2 and 6; R₁₀ is C_(y)H_(2y) with y between 1 and 12 or CH₂CH₂[OCH₂CH₂]_(z)CH₂CH₂ with z between 0 and 10; and R₁₁ is H or OH or OC_(x)H_(2x+1) with x between 1 and 6 or Hal where Hal is Cl, Br, F or I; or an acetoxy group or a sulfonate ester group or an oxo group; all stereoisomers and optical isomers of said formula I or formula II or pharmaceutically acceptable salts thereof.
 2. A method for treating a subject suffering from malaria comprising: administering to said subject an effective amount of a compound of formula (I)

wherein R₁ is H or OC_(i)H_(2i+1) with i between 0 and 6; R₂ is H or OC_(j)H_(2j+1) with j between 0 and 6; R₃ is H or OC_(k)H_(2k+1) with k between 0 and 6; R₄ is H or OH; R₅ is OH or OC_(m)H_(2m+1) with m between 1 and 6 or an acetoxy group or an oxo group; R₆ is OH or OC_(n)H_(2n+1) with n between 1 and 6 or an acetoxy group or an oxo group; R₇ is OC_(p)H_(2p+1) with p between 0 and 6; R₈ and R₉ may be similar or different and represent H or OC_(q)H_(2q+1) with q between 0 and 6, or Hal where Hal is Cl, Br, F or I, or form together a covalent bond whereby the bond is a double bond or an ether bond (epoxy group); R₁₀ is H or C_(r)H_(2r+1) with r between 1 and 12 or an unsaturated alkyl group or a cycloalkyl group (tri- to hexa-) unsaturated or not, with or without heteroatoms; or an aromatic or a polycyclic aromatic group with or without heteroatoms; or C_(s)H_(2s)-A with s between 1 and 12 and whereby A is a saturated or (tri- to hexa-) unsaturated cycloalkyl group, with or without heteroatoms or an aromatic or a polycyclic aromatic group with or without heteroatoms or A is C₆H_(5-t)-(Hal)_(t) with t between 1 to 5 or C₆H_(5-u)—(O—C_(v)H_(2v+1))_(u) with u between 1 to 5 and v between 0 and 6; or R₁₀ represents two substituents similar or different rendering the nitrogen atom quaternized, or an oxygen atom (nitrone group) and in which case the bond between the nitrogen atom and C₉ is a double bond; or R₁₀ represents CH₂CH₂[OCH₂CH₂]_(w)OCH₂CH₂—B with w between 0 and 10 and where B is OH, O-D or NH-D where D is a C₁-C₁₂ alkyl group bearing an electrophilic function such as an isothiocyanate; R₁₁ is H or OH or OC_(x)H_(2x+1) with x between 1 and 6 or Hal where Hal is Cl, Br, F or I; or an acetoxy group or a sulfonate ester group or an oxo group; or R₁₀ and R₁₁ may represent an isoalkylidene group; or, of formula (II):

wherein R₁, R₂, R₃, R₅, R₆, R₂, R₈ and R₉ are defined as above; R₄ is H or OH or OC_(l)H_(2l+1) with 1 between 2 and 6; R₁₀ is C_(y)H_(2y) with y between 1 and 12 or CH₂CH₂[OCH₂CH₂]_(z)OCH₂CH₂ with z between 0 and 10; and R₁₁ is H or OH or OC_(x)H_(2x+1) with x between 1 and 6 or Hal where Hal is Cl, Br, F or I; or an acetoxy group or a sulfonate ester group or an oxo group; all stereoisomers and optical isomers thereof of said formula I or formula II or pharmaceutically acceptable salts thereof.
 3. Chemical compound of formula (I)

wherein R₁ is H or OC_(i)H_(2i+1) with i between 0 and 6; R₂ is H or OC_(j)H_(2j+1) with j between 0 and 6; R₃ is H or OC_(k)H_(2k+1) with k between 0 and 6; R₄ is H or OH; R₅ is OH or OC_(m)H_(2m+1) with m between 1 and 6 or an acetoxy group or an oxo group; R₆ is OH or OC_(n)H_(2n+1) with n between 1 and 6 or an acetoxy group or an oxo group; R₇ is OC_(p)H_(2p+1) with p between 0 and 6; R₈ and R₉ may be similar or different and represent H or OC_(ql H) _(2q+1) with q between 0 and 6, or Hal where Hal is Cl, Br, F or I, or form together a covalent bond whereby the bond is a double bond or an ether bond; R₁₀ is H or C_(r)H_(2r+1) with r between 1 and 12 or an unsaturated alkyl group or a cycloalkyl group (tri- to hexa-) unsaturated or not, with or without heteroatoms; or an aromatic or a polycyclic aromatic group with or without heteroatoms; or C_(s)H_(2s)-A with s between 1 and 12 and whereby A is a saturated or (tri- to hexa-) unsaturated cycloalkyl group, with or without heteroatoms or an aromatic or a polycyclic aromatic group with or without heteroatoms or A is C₆H_(5-t)-(Hal)_(t) with t between 1 to 5 or C₆H_(5-u)—(O—C_(v)H_(2v+1))_(u) with u between 1 to 5 and v between 0 and 6; or R₁₀ represents two substituents similar or different rendering the nitrogen atom quaternized, or an oxygen atom (nitrone group) and in which case the bond between the nitrogen atom and C₉ is a double bond; or R₁₀ represents CH₂CH₂[OCH₂CH₂]_(w)OCH₂CH₂—B with w between 0 and 10 and where B is OH, O-D or NH-D where D is a C₁-C₁₂ alkyl group bearing an electrophilic function such as an isothiocyanate; R₁₁ is H or OH or OC_(x)H_(2x+1) with x between 1 and 6 or Hal where Hal is Cl, Br, F or I; or an acetoxy group or a sulfonate ester group or an oxo group; or R₁₀ and R₁₁ may represent an isoalkylidene group; or a compound of formula (II)

wherein R₁, R₂, R₃, R₅, R₆, R₇, R₈ and R₉ are defined as above, R₄ is H or OH or OC_(l)H_(2l+1) with 1 between 2 and 6; R₁₀ is C_(y)H_(2y) with y between 1 and 12 or CH₂CH₂[OCH₂CH₂]_(z)OCH₂CH₂ with z between 0 and 10; and R₁₁ is H or OH or OC_(x)H_(2x+1) with x between 1 and 6 or Hal where Hal is Cl, Br, F or I; or an acetoxy group or a sulfonate ester group or an oxo group; all stereoisomers and optical isomers of said formula (I) or formula (II), and their pharmaceutically acceptable salts, with the proviso that in formula (I), (1) R₂ is not H or alcoxy when R₃ is OH or alcoxy and R₄ is H or OH and R₅ and R₆ are OH or acyloxy and R₇ is OCH₃ and R₈ and R₉ represent a double bond and R₁, R₁₀ and R₁₁ are H; (2) R₁ is not H when R₂ is H and R₃ and R₇ are OCH₃, R₄, R₅ and R₆ are OH and R₈ and R₉ represent a double bond and R₁₀ and R₁₁ are H; and (3) R₂ is not H or alcoxy when R₃ is OH or alcoxy and R₄ is H or OH and R₅ and R₆ are OH or acyloxy and R₇ is OCH₃ and R₈ and R₉ represent a double bond and R₁ is H.
 4. A pharmaceutical composition comprising a compound according to claim 3, and a pharmaceutically acceptable vehicle.
 5. A pharmaceutical composition comprising a compound of formula (I)

wherein R₁ is H or OC_(i)H_(2i+1) with i between 0 and 6; R₂ is H or OC_(j)H_(2j+1) with j between 0 and 6; R₃ is H or OC_(k)H_(2k+1) with k between 0 and 6; R₄ is H or OH; R₅ is OH or OC_(m)H_(2m+1) with m between 1 and 6 or an acetoxy group or an oxo group; R₆ is OH or OC_(n)H_(2n+1) with n between 1 and 6 or an acetoxy group or an oxo group; R₇ is OC_(p)H_(2p+1) with p between 0 and 6; R₈ and R₉ may be similar or different and represent H or OC_(q)H_(2q+1) with q between 0 and 6, or Hal where Hal is Cl, Br, F or I, or form together a covalent bond whereby the bond is a double bond or an ether bond; R₁₀ is H or C_(r)H_(2r+1) with r between 1 and 12 or an unsaturated alkyl group or a cycloalkyl group (tri- to hexa-) unsaturated or not, with or without heteroatoms; or an aromatic or a polycyclic aromatic group with or without heteroatoms; or C_(s)H_(2s)-A with s between 1 and 12 and whereby A is a saturated or (tri- to hexa-) unsaturated cycloalkyl group, with or without heteroatoms or an aromatic or a polycyclic aromatic group with or without heteroatoms or A is C₆H_(5-t)-(Hal)_(t) with t between 1 to 5 or C₆H_(5-u)—(O—C_(v)H_(2v+1))_(u) with u between 1 to 5 and v between 0 and 6; or R₁₀ represents two substituents similar or different rendering the nitrogen atom quaternized, or an oxygen atom (nitrone group) and in which case the bond between the nitrogen atom and C₉ is a double bond; or R₁₀ represents CH₂CH₂[OCH₂CH₂]_(w)OCH₂CH₂—B with w between 0 and 10 and where B is OH, O-D or NH-D where D is a C₁-C₁₂ alkyl group bearing an electrophilic function such as an isothiocyanate; R₁₁ is OH; all stereoisomers and optical isomers of said formula (I), and their pharmaceutically acceptable salts, provided that R₂ is not H or alcoxy when R₃ is OH or alcoxy and R₄ is H or OH and R₅ and R₆ are OH or acyloxy and R₇ is OCH₃ and R₈ and R₉ represent a double bond and R₁ is H; and a pharmaceutically acceptable vehicle.
 6. The method according to claim 1, wherein the method is for treating a subject suffering from malaria.
 7. The method according to claim 2, wherein the subject suffers from hepatic stage malaria. 